Abstract
Cyanobacteria produce metabolites with diverse bioactivities, structures and pharmacological properties. The effects of microcystins (MCYs), a family of peptide type protein-phosphatase inhibitors and cylindrospermopsin (CYN), an alkaloid type of protein synthesis blocker will be discussed in this review. We are focusing mainly on cyanotoxin-induced changes of chromatin organization and their possible cellular mechanisms. The particularities of plant cells explain the importance of such studies. Preprophase bands (PPBs) are premitotic cytoskeletal structures important in the determination of plant cell division plane. Phragmoplasts are cytoskeletal structures involved in plant cytokinesis. Both cyanotoxins induce the formation of multipolar spindles and disrupted phragmoplasts, leading to abnormal sister chromatid segregation during mitosis. Thus, MCY and CYN are probably inducing alterations of chromosome number. MCY induces programmed cell death: chromatin condensation, nucleus fragmentation, necrosis, alterations of nuclease and protease enzyme activities and patterns. The above effects may be related to elevated reactive oxygen species (ROS) and/or disfunctioning of microtubule associated proteins. Specific effects: MCY-LR induces histone H3 hyperphosphorylation leading to incomplete chromatid segregation and the formation of micronuclei. CYN induces the formation of split or double PPB directly related to protein synthesis inhibition. Cyanotoxins are powerful tools in the study of plant cell organization.
Highlights
The marine and freshwater habitats are considered to be a source of potential drugs
Stimulation of mitosis was observed at low MCY-LR concentrations in several model systems, while inhibition of mitotic activity occurs in long-term treated, non-synchronized root tip meristematic cells of Phragmites australis and Sinapis alba
These alterations are important in the context of chromatin dynamics during mitosis: all of them are correlated with abnormal sister chromatid segregation [103,110,111]
Summary
The marine and freshwater habitats are considered to be a source of potential drugs. To date approximately 16,000 natural products have been isolated from marine, freshwater organisms so it is not surprising that these organisms are a wonderful source of biologically active natural products with diverse chemistry and pharmacology too [1]. In freshwaters the most prominent unicellular organisms are the cyanobacteria which can multiply and can develop huge biomass called as blooms [5] These prokaryotic organisms elaborate the common primary metabolites and pharmaceutically useful compounds and produce toxic substances. Cyanobacterial toxins are classified as hepatotoxins (microcystins and nodularins), neurotoxins (anatoxins and paralytic shellfish toxins), cytotoxins (cylindrospermopsins) and dermotoxins [5] Their production can be found in a diverse range of blue-green species. There are many results and cytogenetic studies relating the effects of these cyanobacterial metabolites especially in animal and human cells, for understanding the whole mechanism or applying as tools in pharmacology, it is important to know the effects in different organisms (animal, plant, fungi) at different levels (histology, cytology, molecular biology). We are focusing in this review on the two main cyanotoxin-MCY and CYN induced changes of chromatin organization and the possible cellular mechanisms of those alterations in plant cells
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